1 82 Purificalion of Aferairy by Agitniion. 



water-gllders, and others, who have occafion to ufe pure mercury, may rejcft fuch as con- 

 tains very little adulteration for want of the chemical apparatus to dillili it. The procefs 

 by agitation, firfl difcovered by Dr. Prieftley, is far from being generally known or ufed ; 

 but will, no doubt, prove an ufcfiil acquilition to many operators. 



This procefs is grounded on the fact, that the metals with which mercury is ufually 

 contaminated, become converted into a black powder by partial calcination when agitated 

 with refpirable air. Take a gl.ifs vial with a ground Hopper* (fuch being generally pretty 

 Itrong), cipalilc of containing lo or 12 ounces of water, and fill about one-fourth of it with 

 tlie foul quickfilver; then putting on the (topper, let the bottle be held inverted with both 

 hands, (haking it violently by (Iriking the liand that fupports it againll the knee. After twenty 

 or thirty (Irokcs, take out tlie Hopper, and blow into the vial with a pair of bellows to change 

 die air. For the purer tl»e air the falter the, procefs advances. After a (liort time, if 

 the mercury be very foul, the furface will not only become black, but a great quantity of 

 the upper part will appear as if coagulated. In this fituation the vial is to be inverted ; 

 and covering the mouth of it with the finger, all the mercury that will flow eafily is to 

 be let out, and the black coagulated part put into a cup by itfelf. The running mercury 

 may be feparated from the black powder, by prefling this mafs repeatedly with the finger. 

 This mercury is to be added to the reft, in order to be agitated again. 



The procefs muft be repeated till no more black matter can be feparated ; and it is not 

 a little remarkable, that the operator will be at no lofs to know when the operation is com- 

 pleted. For the fame quantity of lead feems to come out of it in equal times of agitation, 

 and confequently the whole becomes pure at once. The found of the pure mercury is 

 louder and more harfh than while it contained the adulteration ; fo that by this criterion 

 the end of the procefs is eafily diltinguiftied. 



Dr. PriefUey purpofely diflblved both lead and tin in a large quantity of mercury, which 

 he afterwards purified in this way, and found by fubfequent diftillation, that it had been 

 rendered quite pure. I have myfelf ufed this procefs, which I find cafy and convenient. 

 The laft portions of black matter, which give the mercury a dufty look, are readily fepa- 

 rated by the paper funnel as ufual. 



XIII. 

 jt Memoir containing fame Reftilts arifiug from the ABion of Cold en the Votntile Oils, atnl a:i 

 Examination of the Concretions found in feveraJ of thofe Oils f. By Cit. MARGVERONf 

 Member of the Societi des Pharmaciens at Paris. 



X H £ volatile or eflential oils obtained from vegetable* owe their fluidity, in the fame 

 manner as water, to the portion of caloric they contain. Several of them lofc this ftate at 

 8" above :f the term of aqueous coOgelation (50° Fahrenheit), and afTume the concrete form ; 



• Experiments and Obfcrvations on Air, abridged and methodized, by Jofcph Piieflley, LL. D. F. R. S. 



III.4i9. 



t Annalet de Chimie, XXI. 174. 



X The temperatures in this piper arc according to the fcatc called Reaumur's, in which the freezing point is 

 narked 0°, and the boiling water point 8o*. N. 



Other;, 



